PTL (Patent Literature) 1, and NPL (Non-Patent Literature) 1, and NPL 2 disclose central-management-type path control methods using an OpenFlow technique. The OpenFlow technique disclosed in PTL 1 recognizes communications as end-to-end flows, performs path control on a per-flow basis, and executes load balancing and path optimization.
In PTL 1, NPL 1, and NPL 2, a switch serving as a forwarding node includes a secure channel communicating with a controller (control apparatus) that calculates packet paths. The switch operates in accordance with a flow table set by the controller. In the flow table, a combination of a matching rule which is matched against packet header information and an action describing a processing content applied to packets matching the matching rule is defined. For example, the action is a process of forwarding a packet to a certain interface.
When a switch disclosed in PTL 1, NPL 1, and NPL 2 receives a packet, the switch searches the flow table for an entry having a matching rule that matches header information of the received packet. As a result of the search, if the switch finds an entry matching the received packet, the switch executes a processing content described in the action field of the entry (for example, the switch forwards the received packet to a certain interface).
If the switch does not find an entry matching the packet as a result of the search, the switch requests the controller to set an entry for the received packet. In response to the request, the controller calculates a path for the received packet and notifies switches relating to the path of an entry realizing forwarding that uses the path. Notified of the entry, the switches update the flow tables and execute the processing contents described in the entries in the updated flow tables. Namely, the switches forward the respective received packets.